RFR: 8150044: Generate classlists at build-time

Erik Joelsson erik.joelsson at oracle.com
Wed May 4 14:24:49 UTC 2016

Depends on which OS you are using. You need version 2.69, which is the 
latest. On linux, "apt-get/yum install autoconf" should do the trick 
unless your distribution is ancient. On windows add autoconf through the 
cygwin installer. On mac I think "brew install autoconf" is easiest if 
you are into that. If all else fails, downloading the source [1] and 
building is pretty easy and straightforward too.


[1] http://ftp.gnu.org/gnu/autoconf/autoconf-2.69.tar.gz

On 2016-05-04 16:13, Jim Laskey (Oracle) wrote:
> Correct.  How do I set up autogen so I can apply these changes?
>> On May 4, 2016, at 11:11 AM, Erik Joelsson <erik.joelsson at oracle.com> wrote:
>> Build changes look ok to me, but I also helped write most of them.
>> This certainly adds some build complexity and might seem overly so for just this optimization. As I understand it, the plan is to expand this build time profiling concept to generate more profile data that can be used by for example jlink plugins.
>> /Erik
>> On 2016-05-04 15:36, Claes Redestad wrote:
>>> Hi,
>>> please review this change to generate classlists at build-time
>>> bug: https://bugs.openjdk.java.net/browse/JDK-8150044
>>> webrevs:
>>> top: http://cr.openjdk.java.net/~redestad/8150044/top.01/
>>> jdk: http://cr.openjdk.java.net/~redestad/8150044/jdk.01/
>>> hotspot: http://cr.openjdk.java.net/~redestad/8150044/hotspot.01/
>>> The implementation generates an interim image consisting of a minimal
>>> set of modules, then use this to run a small generator program to
>>> load common utilities and facilities and dump the result of this to a
>>> classlist that is then bundled with the final images.
>>> The smaller number of classes on the default classlist (~1100 instead
>>> of ~2500) requires some adjustment to the metaspace defaults.
>>> This achieves the following:
>>> - Removes a manual, error-prone process to update the versioned
>>>   classlists
>>> - Ensures the classlists shipped with the JDK/JRE is up to date
>>>   with recent JDK changes, e.g., when moving classes from sun.* to
>>>   jdk.internal.*
>>> - Automatically picks up and incorporates the output of jlink plugins
>>>   such as GenerateJLIClassesPlugin into the classlist
>>> - Supports cross-compilation build targets, although it runs using a
>>>   build JDK that can run on the host platform to generate such
>>>   classlists (this isn't ideal, but no worse than the current
>>>   situation, where the versioned classlist for the host platform is
>>>   simply copied to the cross-compiled target)
>>> There are a few concerns/drawbacks:
>>> - It does add complexity to the build, and concern has been voiced that
>>>   this would adversely affect build times. However, I'm happy to say
>>>   that on my machine build times are roughly the same:
>>> Before:
>>> real    2m37.303s
>>> user    35m33.576s
>>> sys    3m46.476s
>>> After:
>>> real    2m36.168s
>>> user    35m31.232s
>>> sys    3m52.268s
>>> (real time varies ± 5s from build to build)
>>> - Startup on the specific applications we've used to generate the
>>>   classlists for previously suffer small regressions. These are
>>>   specifically rather dated AWT and Swing-based applications. OTOH,
>>>   startup characteristics generally improve on other applications
>>>   (minimal VM, jetty, etc...)
>>> Testing: JPRT -testset hotspot
>>> Thanks!
>>> /Claes

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